Field strength calculation according to ITU-R PN525-2

Enter your values here to get an estimate of field strength for your distance to the
transmitter. You must have a clear clear line of sight to the
transmitter. If you don't all bets are off and this calculator is absolutely no
use to you whatsoever.

Note that your results will be of the order of 10-20dB lower than this
predicts. To get the signal strength predicted by this calculator your antenna must be several
metres higher than surrounding obstructions, house roofs etc and have a clear line of sight to the transmitter. Most domestic installations do
not satisfy these requirements, hence assume at least 10dB lower signal
levels.

TX e.r.p. (kW)

distance (km)

UHF channel

frequency (MHz)

wavelength

path loss (dB)

field strength (V/m)

RX antenna gain (dBd)

signal @ aerial terminals (dBuV)

Masthead amp gain (dB) (0 if none)

Downlead length (CT100) (m)

signal @ aerial terminals (dBuV)

The example values are those for my antenna installation, which is a roof level antenna
off a gable end with a clear line of
sight to Sudbury. I measure a signal level of 71-74dBuV for channel 44 using a Promax
cable analyser which is 10-13dB lower than predicted. Which is reasonable given the
typical domestic installation.

Q: I get nowhere near that much signal level. What's up with that then?
A: You don't have line of sight, or nearby obstructions, trees get in the way. If your
aerial is in the loft, there is a loss of 5-25dB going through a typical tiled or slate
roof, and you most certainly are suffering an extra loss due to proximity to water tanks
and clutter which can knock another 5-20dB off your signal level.

How much signal do I need?

It all depends on what you're trying to receive.. Here are the recommendations from the
Confederation of Aerial Installers Code of Practice3
We're assuimng UK practice and a cable impedance of 75 ohms here.